How AI Can Help Businesses Process Invoices and Purchase Orders

Why do invoices and purchase orders take so long?

An invoice is a small document that creates a surprising amount of work. Someone opens the email and downloads the file. Someone types the supplier name, the invoice number, the date, the taxable value, the tax split and the line items into the accounting software. Someone finds the purchase order and checks the rates against it. Someone in the warehouse confirms what actually arrived. If two cartons are short, a phone call starts, and the invoice waits in a tray until that call ends.

None of this is difficult. It is repetitive, it happens hundreds of times a month, and it is easy to get slightly wrong at four in the afternoon on the last day of the month. The cost shows up later, in places that do not look like data entry:

• The same invoice paid twice, once against the emailed copy and once against the courier copy.
• A price increase nobody agreed, paid because the rate was never compared with the order.
• A short delivery paid in full, with the credit note chased months later.
• Early-payment terms missed because the file was still with someone for approval.
• A month-end scramble to find documents that were always going to be needed.

The work worth handing to a system is the reading, the matching and the checking. What stays with people is the judgement: whether a difference is acceptable, whether a supplier should be paid this week, and whether an unusual request is genuine.

What can a system actually read from an invoice or purchase order?

Documents arrive in whatever shape the sender had to hand. A clean PDF produced by the supplier’s billing software. A scan of a printed invoice, slightly skewed. A photograph taken on a phone and sent on WhatsApp, with a thumb over one corner. A purchase order forwarded three times, so the useful page is the third attachment. A system that only reads tidy PDFs will not survive a normal week.

Modern document systems read images and PDFs together and pull out named fields rather than a wall of text. For an invoice, that usually means:

• Supplier name, address and GSTIN, and the buyer details on the invoice.
• Invoice number, invoice date, and any purchase order or contract reference.
• Line items: description, HSN code, quantity, unit, rate and line value.
• Taxable value, the tax split, any discount, freight or packing charges, and the total.
• Payment terms, due date and the bank details printed on the document.

Two properties matter more than the length of that list. First, every value should come with a confidence score, so the system can hold back what it is unsure about instead of guessing. Second, every value should link to the place on the page it was read from, so a reviewer can check it in a second rather than reading the whole document again. That is the pattern behind our Business Operations work, and the same pipeline applies to any document type, as the general document workflow sets out.

How does matching against the PO and goods receipt work?

Matching is the step that turns a read document into a checked one. Two-way matching compares the invoice with the purchase order. Three-way matching adds the goods receipt or delivery note, so you also confirm that what is billed is what arrived. Services often use a two-way match against the order and a signed completion note instead of a receipt.

Real purchasing is untidier than the diagram. One order may be delivered in four lots and invoiced five times. A supplier may bill freight that the order does not mention. A credit note may arrive weeks after the invoice it corrects. So the matching rules need to handle partial receipts, cumulative quantities against a single order, and documents that arrive out of order. Agree how each of those behaves before launch, in writing, with the person who does the work today.

Which checks belong before anything is posted?

Matching answers whether the commercial detail is right. A second set of checks asks whether the document is valid and whether it is safe to act on:

• Is the supplier in your master list, and is the GSTIN on the invoice the one you hold?
• Do the tax lines add up, and is the tax type consistent with the place of supply?
• Is this a duplicate: same supplier, same invoice number, same amount, or the same file seen twice?
• Have the bank details changed since the last invoice from this supplier?
• Is the invoice within the agreed price list, and is the purchase order still open?

The bank-details check deserves its own rule. A changed account number on an otherwise ordinary invoice is one of the more common frauds in accounts payable. Treat it as an exception that a person confirms with the supplier on a number you already hold, never on a number printed on the new document.

India adds one more useful signal. For registered persons above a turnover threshold, invoices for business-to-business supplies must be reported to the invoice registration portal, which returns a unique Invoice Reference Number, a digitally signed invoice and a QR code, as the GST e-invoice portal describes. The threshold has moved over the years: Notification No. 10/2023 – Central Tax substituted the words “five crore rupees” for “ten crore rupees” with effect from 1 August 2023. If your supplier is covered, the presence and consistency of the IRN and QR code is worth checking before you post.

How do tolerances keep exceptions honest?

If every difference of one rupee becomes an exception, your team will spend more time on the queue than they spent on the invoices. A tolerance is a difference you have agreed in advance to accept without a conversation: rounding, a small quantity variance on bulk material, freight within an agreed limit. Write the tolerances down, say who set them and when they will be reviewed, and keep them in one place rather than in each person’s head.

Everything outside tolerance becomes an exception with a reason: price difference, quantity difference, no purchase order, tax mismatch, possible duplicate, supplier not recognised. Reason codes are worth the small effort. After two months they tell you which suppliers, which categories and which internal habits create most of your rework.

Who approves, and what should the audit trail hold?

A system that reads and matches well can still create a governance problem if it is allowed to post and pay on its own. Keep the distinction clear. Preparing a payable is clerical work. Approving it is a financial decision that belongs to a person with the authority to make it, under the same limits and segregation of duties your auditor already expects. The system follows your approval policy; it does not replace it. Design the human decision into the workflow covers what the approver needs in front of them.

The trail behind each record should answer an auditor’s questions without anyone reconstructing the week:

• The original file, where it arrived from, and when.
• Each extracted value, its confidence and the place on the page it came from.
• Which checks ran, and what each one returned.
• What the reviewer changed, and the reason they gave.
• Who approved it, at what time, and under which limit.
• The reference of the record created in your accounting system, and any failed attempt to create it.

That last point is easy to forget. If the connection to your accounting software fails halfway, you need to know whether the entry was created, so nobody posts it twice. Ask how the system prevents a repeated attempt from creating a second record.

How do you measure it, and where should you start?

Measure the current state before you change anything. Take a month of invoices and record how long each took from arrival to posting, how many needed rework, how many were duplicates, how many discounts were missed and how much of month-end was spent looking for documents. Without that, any improvement is a matter of opinion.

• Time per invoice, from arrival to a posted, approved record.
• Share of invoices needing human review, and how that changes month by month.
• Error and rework rate after posting, which matters more than extraction accuracy.
• Duplicates and rate differences caught before payment.
• Cost per completed record, including review time and the software you run.

Start narrow. One document type, one set of suppliers, one team, with review switched on for everything for the first few weeks. Widen the tolerances only when the exception queue tells you the checks are behaving. If you are not sure whether invoices are your best first workflow, the AI Opportunity Blueprint is a paid diagnostic that maps the workflow, assesses readiness and helps you decide what is worth building.